UC Work Capability Forms and Change of Circumstances - Query Appeal Grounds?

Hi, I'm a member here and very grateful for the PIP guides. My adult son has recently been sent the forms for the work capability assessment on the grounds of mental health issues, for which I'm helping him with the wonderful guides here. But another problem has come to light unfortunately!
He moved from his shared flat back home in March and so reported the change of circumstances on his UC journal. Even though he still had to pay rent in his flat because of a fixed tenancy agreement until August, he couldn't claim housing costs here because he doesn't have a tenancy agreement with me etc. But, last week he was told that because he reported his housing cost changes on the last day of his assessment period, ie 16 March which was the day he travelled home, he's going to have to give back all the housing costs for the period 17 Feb to 16 March. If he had said he came home on the 17 March, there would have been no issue with overpayment apparently. I checked the gov.uk info and the relevant page says that 'it can affect payment for the whole assessment period' not that it automatically does or other such wording. It seems crazy that he loses a month worth of housing money when it should only affect the day he reported the change, if it was a fair system...... He's been penalised for not lying I think!

I can't find anything in the Guides that refers to a mandatory reconsideration for this sort of thing. Is it worth doing? Any advice gratefully received, Thanks, Inge

Hi Gary, thank you for your reply and the advice - very grateful for your time and knowledge, thanks, I shall contact the organisations you suggested, Inge